Which texts do you recommend to study universal algebra and lattice theory? As I'm planning to study some algebraic logic (a lot of!), I found that some knowledge of universal algebra, lattice theory and boolean algebras is a must. 
I wonder if you have any recommendation to study from to be well-prepared to study algebraic logic. 
Some of the recommendations I got are: 
$1$-Universal Algebra by George Graetzer. And 
any book on lattices by George Graetzer. 
$2$- Lectures on boolean algebra by Halmos or his new text which is co-authored with Givant.
$3$- Algebraic methods in philosophical logic by Dunn and Hardegree which will gather all the stuff of lattices, universal algebra and boolean algebrs together.
Those are what I got, What do you recommend and why? Any other good books? 
Should I re-ask the same question of philosophy forum? 
 A: You should take a look at George Bergman's book "An Invitation to General Algebra and Universal Constructions". It's also free online, and it's a great introduction to the subject - it works through many concrete examples in Part I before getting to the abstract theory in Part II. 
It doesn't contain much lattice theory, though.
A: Imho, the best modern treatment of universal algebra is
Universal Algebra: Fundamentals and Selected Topics, by Cliff Bergman.
Algebras, Lattices, Varieties, by McKenzie, McNulty, Taylor is a classic and also excellent. Unfortunately, it is out of print, but most university libraries have a copy.
As mentioned by others, Burris and Sankapannavar is good (and free!). While it gives a very nice treatment of most of the basics, it was written a long time ago, and is starting to show its age.  For example, there is little or no clone theory, and no mention of tame congruence theory (which was not invented until 1983).  Fortunately, Cliff's new book has excellent coverage of both clones and tct.
Another list of resources for learning about universal algebra can be found here.
Unfortunately, none of the resources I've mentioned have very much to say about category theory and its relation to universal algebra and lattice theory (although, there is a very brief section in Algebras, Lattices, Varieties presenting categories from a universal algebra perspective).
Finally, since you are just getting your feet wet, I'll mention a couple more introductory references that I came across only recently (so don't know them well, but they look very interesting!) They are by well known/established authors:
Post-Modern Algebra,
by Jonathan Smith and Anna Romanowska
Logical Foundations of Mathematics and Computational Complexity: A Gentle Introduction, by Pavel Pudlak
A: Dunn and Hardegree's Algebraic methods in philosophical logic (2001) is no doubt a great book and very easy to cope with too. It focuses primarily on Algebraic Logic, yet the book's handling of universal algebra is interesting as well.
Another recommendation is the out-of-print A Course in Universal Algebra (1981) by S. Burris and H. P. Sankappanavarin, which is freely available online in its new version and with some corrections by the authors themselves. You can find it for download here.
A: I would like to mention the little known (but excellent) book by W. Wechler, Universal Algebra for Computer Scientists, Springer- Verlag, Berlin (1992).
SBN: 978-3-642-76773-9 (Print) 978-3-642-76771-5 (Online). 
It covers equational theories in great detail but also treats topics that are hardly found elsewhere, like multi-sorted algebras or ordered algebras.
Contents of the book.
1 Preliminaries
Basic Notions (Sets, Algebras
Generation, Structural Induction, Algebraic Recursion and Deductive Systems)
Relations (Regular Operations, Equivalence Relations, Partial Orders, 
Terminating Relations, Well-quasi-Orders, Cofinality, Multiset Ordering 
and Polynomial Ordering).
Trees (Trees and Well-Founded Partially Ordered Sets, Labelled Trees,
$\omega$-Complete Posets and Fixpoint Theorem, Free $\omega$-Completion).
2 Reductions
Word Problem (Confluence Method, Word Problem for Congruences)
Reduction Systems (Abstract Reduction Systems, Term Rewriting Systems, Termination).
3 Universal Algebra
Basic Constructions (Subalgebras and Generation, Images and Presentation, Direct Products 
and Subdirect Decompositions, Reduced Products and Ultraproducts).
Equationally Defined Classes of Algebras (Equations, Free Algebras, 
Varieties, Equational Theories, Term Rewriting as an Algorithmic Tool for 
Equational Theories).
Implicationally Defined Classes of Algebras (Implications, Finitary Implications 
and Universal Horn Clauses, Sur-Reflections, Sur-Reflective Classes, 
Semivarieties and Quasivarieties).
Implicational Theories, Universal Horn Theories, Conditional Equational
Theories and Conditional Term Rewriting.
4 Applications
Algebraic Specification of Abstract Data Types (Many-Sorted Algebras, Initial 
Semantics of Equational Specifications, Operational Semantics).
Algebraic Semantics of Recursive Program Schemes (Ordered Algebras, Strict 
Ordered Algebras, w-Complete Ordered Algebras, Recursive Program Schemes.
Appendix 1 : Sets and Classes.
Appendix 2 : Ordered Algebras as First-Order Structures.
